Studies aimed at developing more useful methods of utilizing the electron beam for quantitative and qualitative measurements of biological entities and the development of appropriate techniques for preparing biological samples for these measurements are being pursued. Specifically these new applications for the electron beam are directed towards understanding structure and function of virus and virus-cell interactions. The scanning electron microscope (SEM) has been utilized to observe the effects of dexamethasone on virus replication and expression on infected cell surfaces. In addition, the SEM has been used to comparatively examine human normal and tumor cells of diverse origin. An image intensification system interfaced to the transmission electron microscope (TEM) has provided the means of studying the structure of unstained virus in thin sections with the ultimate goal being automated computer search and read-out. Immunological tagging with heavy metals to cell surfaces and internal structures have been studied to provide a system for the localization of viral antigenic sites by computer controlled energy dispersive x-ray analysis and mapping of these areas. Collaborative studies requiring advanced techniques of SEM and TEM have been performed with other viral oncology groups.